Street lighting continues to be one of a city's most important and pressing concerns for various reasons. It is very important to try to ensure that adequate lighting is provided for the safety of the pedestrians and motorized and non-motorized vehicle operators and passengers.
Power line carried communications (PLC) are sometimes used for controlling and monitoring street lighting luminaires. PLC may suffer from grounding practices and various impedance mismatch problems such as those encountered when signals transit from one type of power service main to another. Impedance mismatches may result in signal attenuation in crossing the service main transition point, signal reflection resulting in increased interference on the communications signal, and also standing wave phenomena deleterious to PLC communications. If the power line should also serve inductive loads such as fans or air conditioning equipment, capacitor banks may have been installed to correct the power factor. Such capacitor installations may result in severe attenuation of high frequency signals. High frequency signals also experience high attenuation if there is an isolation transformer in the power path, or voltage equalizers such as tap changer transformers. Additional problems are the time changing nature of the PLC channel which may adversely affect its linearity and time invariance for designing signaling sets using techniques implicitly depending upon superposition. Additionally, the communications useful bandwidth of the power line is a function of many parameters including noise. According to the IEEE Standard for Broadband over Power Line Networks, Annex F, power line channels are subject to four classes of noise. They include thermal background noise that is Gaussian and colored, periodic and aperiodic impulsive noise, AM narrowband noise, and noise from other users of the power line qua a communications medium.
Another choice for communications control and monitoring is by wireless non-optical RF communication links. These links are, however, vulnerable to several problems including changing propagation environments due to construction, vehicle movements, and other time-varying communication path impairments. The wireless non-optical RF communication links are also susceptible to degradation due to changing electromagnetic noise characteristics and also potential malicious interference. Such changing environmental aspects may increase the latency of the communications transported on a mesh network, for example, decrease its usable bandwidth, and concomitantly reduce its throughput. Additionally, operational problems with wireless non-optical RF mesh networks have been reported including difficult maintenance from management complexities, antenna design and successful operation under real-world conditions. Problems include implementation and maintenance issues, protocol problems and discovered deficiencies under scaling and unanticipated interference scenarios.
An additional consideration requiring attention has to do with the nature of the light production itself. Conventional lighting is costly to operate and to maintain. It is for this reason that many city infrastructure authorities have decided to either replace or newly install street lighting that is LED-based. It is important that the individual luminaires of a street lighting installation be monitored in order to determine continued and proper functioning. One of the challenges with LED lighting is that it differs from conventional lighting in a way that may make it more difficult to assess its functional condition. This difference is in the ageing process. A conventional lamp may be considered to be in one of two states: either functional or non-functional (burned out). When a conventional lamp burns out it draws no current. An LED on the other hand becomes dimmer as it ages and there is no change in electrical current that may be directly monitored to assess the condition of the LED.
There is therefore a need to develop alternative control communication techniques and better systems and methods for assessing the condition of street lighting led-based luminaires, and reporting and subsequently locating the luminaires whose light production is below a specified threshold.